Computer input devices such as mice have been the mainstay device for most users interacting with a computing system. The mouse, as the principal computing navigation device, has evolved over recent years from the basic tethered single function mechanical pointing device using a surface contact ball to the wireless optical multi-function input device of today that can employ laser/LED light sources and image sensors. The control of inadvertent pointer tracking was solved in a straightforward way with the ball mouse, since when the user clutched the mouse from the tracking surface, the ball simply dropped away from the internal contract-driven linear tracking mechanism. However, along with this optical “sophistication” come additional problems such as processing reflected light from a variety of different navigation (tracking) surfaces and controlling tracking when the mouse leaves the tracking surface.
Clutch height is a parameter that must be addressed for control in an optical mouse. As the mouse is lifted off of the tracking surface, it is desirable to cease mouse tracking after a specified distance has been reached. Put differently, the user does not want to see the mouse pointer moving randomly on the display. This problem becomes particularly poignant for computer users that demand precise tracking control when moving the mouse off the tracking surface, such as for computers gamers, CAD operators, for example.